Tube-mill.



"J. S. FASTING.

TUBE MILL.

APPLICATION FILED APR-28.1915.

Patented, Nov. 14, 1916.

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J. S. FASTING.

TUBE MILL.

APPLICATION FILED APR.28. 1915.

1 $04 554 Patented Nov. 14, 1916.

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are STAES PA JOHAN S. FASTING, 0F FREDEBIKSBERG, NEAR COPENHAGEN, DENMARK, ASSIGNOR TO F. L. SMID'IH & (10., OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

TUBE-MILL.

Specification of Letters Patent.

Patented Nov. 14, 1916.

Application filed April 28, 1915. Serial No. 24,437.

mark, have invented certain new and useful Improvements in Tube-Mills, of which the following is a specification, reference being had to the accompanying drawings, forming a part hereof.

This invention relates to tube mills with continuous feed and discharge, and charged with free grinding bodies. In mills of'this general character, there is always a slippage between the charge and the mill when the mill is rotated, which slippage reduces the efficiency of the machine. In mills with comparatively smooth linings and operating at moderate speeds the slippage has generally been reduced by increasing the charge in the mill. This method, however, has the disadvantage that the weight on the bearings is materially increased, thus increasing also the friction losses and increasing the power required to operate the mill, and it has the further disadvantage that the wear on the grinding bodies is very high owing to the heavy charge in proportion to the output. It has been attempted to reduce the charge and secure proper lifting action in the mill by means of longitudinal ribs or bars or by steps on the lining such as corrugations, and also by projections on the lining or dents or depressions in it, which would help to lift the charge in the mill to the proper point. This method suflers from the disadvantage that it throws and tumbles the grinding bodies among one another in an irregular manner which, in accordance with past experience, tends to reduce the grinding efficiency of the machine. In later practice it has been attempted to reduc e this slippage by increasing the speed of the machine, and in this manner to make use of the increased centrifugal force to lift the grinding bodiesup to the proper point. This results in a more eflicient grinding action than is obtained in mills of the first mentioned class, particularly by the lifting of the grinding bodies to a point very close to the zenith of the mill and the throwing of them across the grinding'drum in a continuous stream, with the material, against the opposite side of the machine, and thereby materially increasing the efficiency of the apparatus. The higher speed of the drum in this case, however, naturally will increase the friction losses in the main bearings and the wear on the operating gear as well as the power to operate the mill.

, The object of the present, invention is to overcome these disadvantages by employing other means to carry the grinding bodies up to the proper point than by increasing the charge or the centrifugal force, or by employing longitudinal bars or projecting knobs or pockets to throw and toss the grinding bodies aboutin the mill, and thus by decreasing the charge of grinding bodies and avoiding very high speed to decrease the friction losses as well as the wear of the grinding bodies.

The present invention further has as its object to cause the grinding bodies to operate in the most eflicient manner in the mill by lifting them up to the proper point and causing them to move in a continuous stream, together with the material, down over the ascending mass of grinding bodies and material toward the bottom of the mill.

To accomplish this there are introduced into the mill members which increase the frictional drag between the mass of the grinding bodies and the mill in a direction parallel to the path of the ascending grinding bodies, and tend to lift the grinding bodies to a sufficient height, and there release them so that they shall move continually in a solid transverse stream and be caused to grind the material without being tossed about in the mill in various directions in the manner described above and by methods which haveproved inefficient. The

frictional members introduced into the maeflicient operation either with respect to the travel of the material through. the mill or with respect to the steady and uniform grinding of the material. In fact it has been shown that the improved mill. possesses certain advantages in practice which are not to be obtained under all conditions of use by the old. method of securing the hammering action as in mills of the second class as men tioned above.

structurally the improved mill is of the usual form save that several circumferential ribs or flanges, either continuous or interrupted, are disposed on its inner wall in planes atright angles to the axis of the mill to form partitions to separate'thegrinding bodies and material into parallel, transverse streams. These ribs or flanges or partitions are so disposed with respect to each other that the grinding bodies and material between them, besides the frictional support afforded by the shell, also receive a frictional support laterally against the ribs or flanges or partitions, so as, either by a bridging or arching action or by an increased frictional drag, materially to increase the slippage between the charge and the mill. The flanges or ribs or partitions may be made still further to increase the grip or frictional drag between the engaged grinding bodies and material and the mill and yet permit the free movement of the material longitudinally through the mill, as by perforating the partitions or forming each as an interrupted circumferential series of de- 'tached or separated plates or blades.

The ribs or flanges or partitions are preferably made relatively thin, so as to cause as little disturbance to the natural motion of the grinding bodies as possible, and preferably with large lateral faces against which the grinding bodies and material rest, so as to increase as much as possible the frictional grip or drag between the mill and the charge of grinding bodies and material, and also at the same time to increase the total surface of the mill with which the grinding bodies come in contact, as this also tends to increase the efficiency of the apparatus. The preferred forms of the ribs and flanges and the relative dispositions thereof with respect to each other to effect the'desired results, will appear more particularly hereinafter as the description, proceeds, reference now being vided with internal ribs or partitions of slightly modified form. Fig. 4c is a View in longitudinal section of the mill illustrated in Fig. 3. Fig. 5 is a view in transverse section taken through a mill provided with still another form of internal flanges or partitions', and Fig. 6, is a longitudinal section of the mill illustrated in Fig. 5. r

The mill at shown in the drawings may be of usual form and be capable of operation under the usual conditions and speed of grinding. On the inner wall of the mill there are provided, in the embodiment shown in Figs. 1 and- 2, several circumferential series of relatively thin transverse plates or flangesb, spaced from each other to divide the mill, adjacent the circumferential wall, into circumferential channels. The plates of one series are set so as to lap the spaces between the plates of the next series to facilitate the travel of the material longitudinally through the mill. These plates or flanges Z) are disposed at right angles with respect to the axis of the mill,-and extend inwardly from the wall of the mill for a suitable distance to divide the mass of grinding bodies and material, into parallel transverse streams and create frictional drag between the mass and the mill forming annular channels, but it will be understood that the radial extension of the plates may be varied so as to give the greatest possible effect in reducing slippage and lifting the charge. The gist of the invention resides in the provision of the flanges or plates or ribs Z), or the equivalents thereof, to form partitions to separate tl e material and grinding bodies into parallel transverse streams and thereby increase the 1 will leave the wall of the mill and fall upon the material at the bottom, in parallel trans verse streams, or the partitions may be at such distances that there shall be only a sub stantial reduction of slippage with no bridging action. Of course, the speed of rotation of the mill will be such as to tend to carry the grinding bodies and the material. part of the way up from the lowest point to the highest, but the resulting centrifugal force at the preferred speed, is not sufiicient to carry the charge of material and grinding bodies up to a point wherethe most efficient grinding action will ensue when gravity prevails. Such lifting is accomplished, at comparatively low speed, by the increased frictional drag afforded by the circumferential partitions. It will be noted from Fig. 2 that the longitudinal movement of the material through the mill is not interfered with because of the spaces between the plates 6 in each circumferential series.

In the embodiment illustrated in Figs. 3 and 4, circumferential annularly arranged and extended ribs B are employed, and each rib is spaced from one another circumferentially to form a series of openings 0, which enhance the frictional drag and also permit the material to pass freely in its longitudinal movement through the mill. The spacing of the ribs B with respect to each other may be as described with respect to Figs. 1 and 2, such that the grinding bodies and the material will bridge or arch between the ribs and thereby be carried up with the wall of the mill nearly to the zenith, where the material and grinding bodies under the influence of gravity will fall toward the lower part of the mill, or such that they will act frictionally on the material, without causing a bridging action, and so cause the mass to be raised to a higher point than would be possible otherwise. In this form of the invention the inner ends of the ribs B are united by an annular closing member I).

In Figs. 5 and 6' another embodiment of the invention is shown, in which the mill at is provided with circumferential rows of radially disposed flanges or thin fiat blades 01 (as in Figs. 3 and l) of a thickness only suflicient to give them the required strength and a radial length which will practically engage the layer of grinding bodies and material on the ascending side of the mill. These rows of blades are disposed in continuous, parallel, circumferential series as described with respect 'to the plates or flanges 7) and b. The blades cl permit the material to pass freely between them in its longitudinal movement through the mill, while exerting such frictional drag upon the material and grinding bodies that .the material and grinding bodies are carried up with the ascending wall of the mill in the manner hereinbefore described.

In the operation. of the improved mill the material and grinding bodies lie between the partitions at the bottom and, as the mill rotates are carried up with the wall of the mill beyond the point at which the centrifu gal force is effective and to a point where gravity prevails, and thus travel in parallel, transverse streams downward toward the opposite side of the mill, whereby the material is ground between the grinding bodies. During the operation of the mill the material and grinding bodies fall in streams 1n the manner described and not in successive masses as would be the case where longitudinal ribs or corrugations are employed, and will not be tossed about in the mill in various directions as would be caused by irregularly spaced knobs and protrusions or pockets on or in the wall of the mill, but will descend in parallel, transverse streams, and thematerial will therefore be ground uniformlyand continuously. The partitions for assisting in the lifting of the mass are not such as to interfere with the continuous movement of the material through the mill.

The ribs or flanges or partitions may be changed in form and number without departing from the spirit of this invention, provided they are so shaped and disposed with respect toeach other as to be effective in affording substantial frictional drag for the mass and carrying it to a point where an effective action of the grinding bodies on the material will result.

I claim as my invention:

1. An improvement in the art of grinding in grinding mills which consists in producing in said mill a slowly rotating mass of grinding bodies and material to be ground, applying closely related annularly arranged and extended frictional lifting ribs having surfaces extending in the direction of rotation to said mass while rotating and causing a free longitudinal feeding of said mass at points below the inner surface of said rotating mass.

2. A grinding mill for grinding with free grinding bodies provided with closely related series of parallel, circumferential annularly arranged and extended ribs along its inner wall, spaced from one another circumferentially to provlde openings below the inner periphery of said ribs'which ribs serve to separate the charge into parallel, transverse streams, provide communicating channels between such ribs for free longitudinal feeding of the material and afford lateral support for the charge at the sides of such streams.

3. A grinding mill for grinding with free grinding bodies provided with closely related series of parallel, circumferential annularly arranged and extended ribs along its inner wall, which serve'to separate the charge into parallel, transverse streams, said ribs being spaced from one another to provide substantially radially extended opening's therebetween below the inner edge of said ribs to increase the frictional drag of the lateral faces at the sides of said streams and permit free longitudinal feeding movement of the material in the mill.

4. A grinding mill for grinding with free grinding bodies provided with closely related series of parallel, circumferential, an-

nularly arranged and extended ribs along its inner wall, spaced from one another circumferentially to provide openings below the inner periphery of said ribs which ribs serve to separate the charge into parallel, transverse streams, provide communicating channels between such ribs for free longi- This specification signed and witnessed fudinzil feeding fof the material and afikrd this 10th day of April A. D., 1915.

atera support or the charge at the si es T of such streams, and an annular closing 4 JOHAL FASTING' member united with said ribs at their inner Signed in the presence 0:t'

ends and providing a free and unobstructed CHR. ENGELHART, axial passageway. MIKAEL VOGEL-JORGENSER.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

